@Tom, very easy to solve: just delete you answer, ephilip was quicker. and you better be quick, before you get two more downvotes, or the next badge you earn won't be a nice one :)
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Molly7244Sep 11 '09 at 22:57

1

What's this???? Somebody tried to HELP writing an answer, the phone rings, he puts the caller on hold, posts the message and two minutes later is insulted by a child hysterically pointing out HE WAS FIRST!!! and ... what? an admin? threatening him? Is this a forum to help or just show of and insult people?? TomWij, my sympathy goes with you.
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WolfSep 11 '09 at 23:09

You can apparently use Windows Movie Maker to add watermarks to videos.
See this article : Watermark in Windows Movie Maker, and make sure to read the comments as well.
I haven't done this myself, so can't vouch for the process, but there are many testimonies to it on google.